cb750 sputtering

[frank]

i have a 1980 cb750c my battery isnt holding a charge, its sputtering when the motor is hot then it backfires when i let go of the throttle. i cleaned the jets, carbs and new plugs. i need some help

[Re-run]

Well first off, the charging issue.
How new is the battery and what type is it? If it is a few years old, it my not hold a charge or it may need water if it is a standard lead acid battery. If water is ok, then charge it up and let it sit overnight and check voltage. If it drops below 12 then the battery is shot. If the battery holds charge, then put it in the bike and start the bike. Rev to about 3000 rpm and check voltage. If it is very low 12 or under, then your system is not charging. If it is 13 or over, then you should be good for charging and may just not be holding enough rpm to charge.

As for the sputtering, After the bike is warm, pull the plugs and see what color they are. If the plugs are really dark, then it is too rich. If white, then too lean.
Also check the timing to make sure it is correct.
Also, what air filter do you have right now.

[woodsrider250]

These bikes are known for failing alternators.  They will also run like crap with a bad one, battery getting low (CDI ignition).

[Re-run]

I knew about bad alts but I didnt want to scare the guy right away!

I was not aware that it would cause the bike to run like crap though. Poor charging or none only affects the sohc when the battery voltage drops too low so this is a good thing to know.

[cb]

i started taking off starter\ reg when i noticed that it had some black tar like that had melted then dripped down. at first i thought it was the starter\reg then i took off both
CDI IGNITION MODULE CONTROL i looked underneath and that the black stuff came from there. my question is if anyone can show me a picture of the bottom part of a cdi imc to see what its suppose to look like, and my other question is would that be the cause of my charging problem?

[billod2GPEK]

FAILING IS RIGHT i have replaced two rotos and two reg rect along the rotors. even replaced the stator. 1980 cb 750. & no there is no shorts, or bad ground. spark igniters dont look so great but at 100.00 bucks a pc. & i have 2 they will have to wait.

[billod2GPEK]

they all look melted mine to. charging may be your rotor i have replaced 2 you have to take a oms reading acrossed the two slip rings to tell and reading at all 3 yellow wires if bad replace both reg-rect & rotor a same time cause one can take out the other

[vern401]

smooth black almost plastic feel to them. no cracks etc. the black is a sealer used to protect from moisture.